In general, for example, a wheel loader is known as a representative example of a wheel type construction machine. In this wheel loader, a front vehicle body having front wheels and a rear vehicle body having rear wheels are connected through a connecting mechanism to be capable of swinging in the left-right direction. A working device including a loader bucket and the like is attached on the front vehicle body, and a cab, an engine, a power transmission device, a hydraulic pump and the like are mounted on the rear vehicle body.
Traveling axle devices are mounted respectively on the front vehicle body and the rear vehicle body of the wheel loader to rotate left and right wheels, and rotation of an engine is transmitted through a vehicular power transmission device to the axle devices. Therefore, the left and right wheels rotate to cause the wheel loader to travel. The traveling axle device is configured of a casing having a differential case and left and right axle tubes extending from the differential case to both the sides in the left-right direction, a differential mechanism provided in the differential case of the casing, left and right axle shafts provided in the respective axle tubes of the casing to transmit rotations distributed by the differential mechanism to the left and right wheels, and left and right brake mechanisms for imparting braking forces to the left and right axle shafts.
Reduction gear cases are disposed on the wheel sides of the left and right axle tubes, and planetary gear reduction mechanisms are respectively disposed in the reduction gear cases. The planetary gear reduction mechanism reduces the rotation of the axle shaft, which will be transmitted to the wheel. Lubricating oil is filled in the reduction gear case to lubricate the planetary gear reduction mechanism and the like. This lubricating oil is sealed by an oil seal disposed in the reduction gear case (Patent Documents 1 to 3).